Rubber Member, Tire, and Method of Manufacturing Rubber Member

ABSTRACT

A vehicle tire, as a rubber member, includes, on at least a part of the surface thereof, a fine ridged/grooved structure formed via transfer from a mold and having fine ridged/grooved portions arranged at a constant arrangement pitch, wherein a region in which the fine ridged/grooved structure is provided is visually recognizable by a different structural color from the colors of other regions. The fine ridged/grooved structure is formed on a sidewall portion of the vehicle tire, and the region in which the fine ridged/grooved structure is provided is formed in a shape to display predetermined information.

TECHNICAL FIELD

The present technology relates to a rubber member, and a tire, whichhave a region that produce a color via a structural color, and a methodof manufacturing the rubber member.

BACKGROUND ART

In the related art, to impart information such as alphanumerics andmarks to the surface of a rubber product such as a tire, ink has beendeposited to the rubber surface by means of an inkjet printer, to printthe information thereon.

Alternatively, a structure color produced by a fine structure that isequal to or smaller than a light wavelength has been known and appliedto various fields.

For example, Japan Unexamined Patent Publication No. 2009-192676discloses a color filter that produces structural colors. Japan PatentNo. 4925025 discloses the technique of calculating a distortion of anobject by measuring a change in produced structural colors (wavelengthchange). In Japan Unexamined Patent Publication No. 2009-192676, thefine structure that produces the structural colors is formed bystamping, and in Japan Patent No. 4925025, the structural color isproduced by periodically arranging microparticles on the surface of anelastic body.

In a case where information is printed on a tire by the use of an inkjetprinter as in the above-described related art, the ink is graduallypeeled off from the rubber surface due to expansion and contraction(deflection) of the rubber during driving. Thus, it is difficult tomaintain the printed information to be visually recognizable for anextended period of time.

As described above, the structural color has been applied to variousfield. However, the method of forming the fine structure that producesthe structural color by stamping and the method of laminating aplurality of layers to produce the structural color, as described inJapan Unexamined Patent Publication No. 2009-192676, are applied toproducts having a thin-film structure, such as a color filter.Additionally, such methods often serve to produce the structural colorby utilizing transmitted light (diffracted light) and therefore, cannotbe directly applied to a less transparent rubber member such as a tire.

Further, the method of arranging microparticles to produce thestructural color as described in Japan Patent No. 4925025 cannot beeasily applied to members requiring heating that may cause deformationof the members, such as vulcanization in the tire manufacturing process.

SUMMARY

The present technology imparts information that will be visuallyrecognizable for an extended period of time on the surface of the rubbermember.

A rubber member according to the technology includes a fineridged/grooved structure on at least a part of the surface of the rubbermember, the fine ridged/grooved structure formed via transfer from amold and having fine ridged/grooved portions arranged at a constantarrangement pitch; a region in which the fine ridged/grooved structureis provided is visually recognizable by a different structural colorfrom the colors of other regions.

In the rubber member according to a further aspect of the technology,the arrangement pitch or ridge/groove height of the fine ridged/groovedportions is determined based on a wavelength of visible light, thewavelength corresponding to the color visually recognizable as thestructural color.

In the rubber member according to a further aspect of the technology,the arrangement pitch or ridge/groove height of the fine ridged/groovedportions is equal to or smaller than 650 nm.

A tire is made of a rubber member according to a further aspect of thetechnology.

In the tire, the fine ridged/grooved structure is formed on a sidewallportion, and the region in which the fine ridged/grooved structure isprovided is formed in a shape to display predetermined information.

In the tire, the sidewall portion contains a diene rubber, a carbonblack, and a silica, the diene rubber contains from 30 to 70 mass % ofnatural rubber and/or isoprene rubber, a nitrogen adsorption specificsurface area of the carbon black is from 20 to 60 m²/g, a content of thecarbon black is from 5 to 45 parts by mass per 100 parts by mass of thediene rubber, a content of the silica is from 15 to 55 parts by mass per100 parts by mass of the diene rubber, and a total content of the carbonblack and the silica is from 30 to 60 parts by mass per 100 parts bymass of the diene rubber.

A method of manufacturing a rubber member according to the technologyincludes: forming a mask on which pattern structures are arranged at theconstant pitch; arranging the mask on a substrate made of a metal or asemiconductor material and etching the substrate; and adheringunvulcanized rubber to the substrate, vulcanizing the unvulcanizedrubber, and transferring the fine ridged/grooved structure to thesurface of the vulcanized rubber.

The method of manufacturing the rubber member according to a furtheraspect of the technology further includes determining the arrangementpitch of the fine ridged/grooved portions based on a wavelength ofvisible light, the wavelength corresponding to the color visuallyrecognizable as the structural color, and in the forming the mask, thepitch of the pattern structures is determined based on the arrangementpitch determined in the determining the arrangement pitch.

The method of manufacturing the rubber member according to a furtheraspect of the technology further includes determining the ridge/grooveheight of the fine ridged/grooved portions based on a wavelength ofvisible light, the wavelength corresponding to the color visuallyrecognizable as the structural color, and in the etching, an etchingtime of the substrate is appropriately controlled to match theridge/groove height of the ridged/grooved portions with the ridge/grooveheight determined in the determining the ridge/groove height.

According to the technology, in at least a part of the rubber member, astructural color exhibits a color that is different from the colors ofother regions. Thus, the durability of an indicator on the rubbersurface is advantageously improved compared to a case where theindicator is drawn using ink or the like.

According to the technology, information may be indicated in any coloron the surface of the rubber member by appropriately modifying thearrangement pitch or ridge/groove height of the fine ridged/groovedportions.

According to the technology, information may be displayed in any colorincluding red.

According to the technology, information may be indicated in thestructural color on the tire surface. Thus, the indicator isadvantageously employed with high durability against wear caused by theuse of the tire.

According to the technology, information may be advantageously indicatedin the structural color with high durability on the sidewall portion.

The sidewall portion is easily visually recognizable in the tire fromoutside and has conventionally been used to indicate various informationabout the tire.

According to the technology, information may be advantageously indicatedin the structural color on the surface of rubber having high resistanceto deformation, which is suitable for the sidewall portion.

According to the technology, in at least a part of the rubber member, aregion can be formed, in which a structural color exhibits a color thatis different from the colors of other regions. Thus, the durability ofthe indicator on the rubber surface is advantageously improved comparedto a case where the indicator is drawn using ink or the like.

According to the technology, the arrangement pitch of the fineridged/grooved portions may be advantageously set to any dimension.

According to the technology, the ridge/groove height of the fineridged/grooved portions may be advantageously set to any dimension.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view illustrating a vehicle tire 10 according to anembodiment.

FIGS. 2A and 2B are partial enlarged views of a logo mark 204.

FIG. 3 is a table showing the results of the durability test on thepresent technology and the conventional art.

DETAILED DESCRIPTION

A rubber member, a tire, and a method of manufacturing the rubber memberaccording to a preferred embodiment of the present technology aredescribed in detail below with reference to accompanying drawings.

In the present embodiment, an example of application of the rubbermember according to the present technology to a vehicle tire isdescribed.

FIG. 1 is a side view illustrating a vehicle tire 10 according to theembodiment of the technology.

The vehicle tire 10 includes a tread portion 14 having a tread surfacethat makes a contact with a road surface, a bead portion 16 engaged witha wheel (not illustrated), and a sidewall portion 12 that connects thetread portion 14 to the bead portion 16 and constitutes a tire sidesurface.

In the tread portion 14, wear resistance is important, while in thesidewall portion 12, the resistance to deformation caused by loadsduring driving is important. Thus, the composition in the sidewallportion 12 is different from that of the tread portion 14.

Describing in more detail, in the present embodiment, the sidewallportion 12 contains a diene rubber, a carbon black, and a silica, thediene rubber contains from 30 to 70 mass % of natural rubber and/orisoprene rubber, a nitrogen adsorption specific surface area of thecarbon black is from 20 to 60 m²/g, a content of the carbon black isfrom 5 to 45 parts by mass per 100 parts by mass of the diene rubber, acontent of the silica is from 15 to 55 parts by mass per 100 parts bymass of the diene rubber, and a total content of carbon black and silicais from 30 to 60 parts by mass per 100 parts by mass of the dienerubber.

Various information is indicated on the sidewall portion 12.

Examples of the information indicated on the sidewall portion 12 includea manufacturer name 202 of the vehicle tire 10, a logo mark 204, a tirebrand name 206, a tire dimension 208, a uniformity mark 214, and a lightpoint mark 216. Examples of the information also include a tire serialnumber and a rotation direction.

Among the above-described information, the uniformity mark 214 and thelight point mark 216 are imparted using ink or the like, after thecompletion (vulcanization) and inspection of individual tires.

The manufacturer name 202, the manufacturer logo mark 204, the tirebrand name 206, and the tire dimension 208 are imparted by transferringridges/grooves formed on a mold during vulcanization of the vehicle tire10.

The information transferred from the ridges/grooves of the mold, otherthan the logo mark 204, has the same color as the whole vehicle tire 10,and is visually recognizable by the ridges/grooves on the surface of thesidewall portion 12.

In contrast, the logo mark 204 is in a different color such as themanufacturer's corporate color, and visually recognizable from the colorof the vehicle tire 10.

FIG. 2 are partial enlarged views of the logo mark 204. FIG. 2A is aperspective view, and FIG. 2B is a cross-sectional view taken along A-A.

A fine ridged/grooved structure 30 is provided on the entire region ofthe logo mark 204.

The fine ridged/grooved structure 30 is configured such that fineridged/grooved portions 34 are arranged on a tire surface 32 at aconstant arrangement pitch. The region in which the fine ridged/groovedstructure 30 is provided is visually recognizable due to a differentstructural color from other regions.

The fine ridged/grooved portions described herein refer to various knownstructures used to produce the structural color, such as protrusions andholes. In the present embodiment, they are fine projections protrudingfrom the tire surface 32 that is a curved surface (or a flat surface).

The arrangement pitch described in the present embodiment refers to adistance between centers of adjacent fine projections, that is, pitch.As represented by a sign L in FIG. 2B, the pitch corresponds to a totallength of each one of the projections and each one of the recessedportions along the surface of the rubber member (tire).

The constant arrangement pitch described herein refers to various knownpitches used to produce the structural color, and may be a constantvalue over the entire fine ridged/grooved structure 30, or may varycontinuously or gradually.

The arrangement pitch or the ridge/groove height of the fineridged/grooved portions 34 is determined based on a wavelength ofvisible light, which corresponds to the color visually recognizable asthe structural color. In other words, the wavelength corresponding tothe color to be exhibited as the structural color is selected from awavelength range of the visible light, and a specific dimension of thearrangement pitch or the ridge/groove height of the fine ridged/groovedportions 34 is determined according to the principle of resonancegrating.

In the present embodiment, the arrangement pitch or the ridge/grooveheight of the fine ridged/grooved portions 34 is set to be equal to orsmaller than 650 nm, for example. This is because the experimentsconducted by the present inventors demonstrated that the structuralcolor is recognizable for the fine ridged/grooved structure 30 havingthe arrangement pitch or the ridge/groove height of 650 nm or less.

In the present embodiment, the fine ridged/grooved portions 34 include acylinder extending perpendicularly to the tire surface 32. A top surface3402 of the cylinder is a perfect circle, the diameter R of which isabout 5 μm. A distance S between the adjacent cylinders is 1 μm, and thearrangement pitch is about 6 μm. For the sake of convenience, FIG. 2 donot illustrate the elements in actual ratio.

Here, the present inventors made a plurality of rubber members, whereina height (ridge/groove height) H of each of the fine ridged/groovedportions 34 from the tire surface 32 is different for each of the tires,while the arrangement pitch of the fine ridged/grooved portions 34 aswell as the diameter of the cylindrical fine ridged/grooved portions 34are fixed to the constant values. As a result, following structuralcolors were visually recognized in decreasing order of recognizablearea. The reason why a plurality of colors are visually recognized isthat the structural color varies depending on a viewing angle.

Ridge/groove height of 650 nm: red, magenta

Ridge/groove height of 607 nm: magenta, red, orange

Ridge/groove height of 577 nm: magenta, orange

Ridge/groove height of 536 nm: orange, magenta

Ridge/groove height of 500 nm: yellow, green, orange

As the ridge/groove height was smaller, the color became more bluish.

In this manner, information may be indicated in any color on the rubbersurface by adjusting the arrangement pitch or the ridge/groove height ofthe fine ridged/grooved portions 34. For example, to indicate the logomark 204 in red, the ridge/groove height may be set to about 650 nm.

Next, a method of manufacturing the rubber member producing thestructural color will be explained.

The below-described method of manufacturing the rubber member includes astep of forming a mold having fine pattern structures (step 1 and step2: mold forming step) and a step of adhering unvulcanized rubber to themold, vulcanizing the unvulcanized rubber, and transferring a fineridged/grooved structure to the rubber surface (step 3: transferringstep).

Prior to the following steps, the color of the structural color to beformed on the rubber member is determined, and the arrangement pitch orthe ridge/groove height of the fine ridged/grooved portions isdetermined based on the wavelength of visible light, which correspondsto the determined color (color visually recognizable as the structuralcolor on the rubber member) (an arrangement pitch determining step or aridge/groove determining step).

(Step 1) A mask on which pattern structures are arranged at a constantpitch is formed to form the fine ridged/grooved structure 30 on therubber surface (mask forming step).

First, a chromium (Cr) film of about 80 nm is formed on a mask formingsubstrate (silicon substrate) using a sputtering device. Next, apositive-type electron beam resist is coated on the chromium film byspin-coating (3 seconds at 300 rpm followed by 60 seconds at 4000 rpm).Then, the substrate coated with the electron beam resist is pre-bakedfor 3 minutes on a hot plate at 150° C., and is subjected to exposureand patterning by an electron beam lithographic device. After that, thesubstrate is immersed in a developing solution for 60 seconds to bedeveloped. In a case where the arrangement pitch of the fineridged/grooved portions is determined based on the wavelength of visiblelight corresponding to the color visually recognized as the structuralcolor, that is, the arrangement pitch of the fine ridged/groovedportions is used as a parameter for determining the structural colorbeing produced, the arrangement pitch of the pattern structures in thepatterning is determined based on the arrangement pitch determined inthe arrangement pitch determining step. After development, the substrateis immersed in a mixed-acid chromium etching solution for about 60seconds to selectively dissolve off the exposed Cr, thereby making amask (photo mask).

(Step 2) A mask is placed on a substrate made of a metal orsemiconductor material, and the substrate is etched (etching step).

In the present embodiment, a single-crystal silicon substrate is used asthe above-mentioned substrate. The substrate is cleaned with ultrasoniccleaning for 5 minutes in acetone and methanol in this order, and apositive photoresist is coated on the substrate by spin-coating (3seconds at 300 rpm and then, 60 seconds at 5000 rpm). Next, thespin-coated substrate is pre-baked on a hot plate at 95° C. for 90seconds. The pre-baking evaporates off an organic solvent present in theresist and thus can improve the resist adhesion to the substrate.Subsequently, the substrate coated with the photoresist is exposed usinga mask aligner and the photo mask manufactured in the step 1, and isimmersed in a developing solution to dissolve off the exposed sectionfor patterning.

After patterning, the substrate is etched using a dry etching device(passivation gas: C₄F₈, 80 sccm, etching gas: SF₆, 130 sccm, Boschprocess) to manufacture a mold (silicon mold). In a case where theridge/groove height of the fine ridged/grooved portions is determinedbased on the wavelength of visible light corresponding to the colorvisually recognizable as the structural color, that is, the ridge/grooveheight of the fine ridged/grooved portions is used as a parameter fordetermining the reproduction of the structural color, the ridge/grooveheight of the ridge/groove portions can be matched with the ridge/grooveheight determined in the ridge/groove height determining step byappropriately controlling an etching time of the substrate.

In the above-mentioned step 1 and step 2 (mold forming step), the moldhaving the fine ridged/grooved structure is manufactured byphotolithography. However, the method of manufacturing the rubber memberaccording to the present technology is not limited to this, and may bevarious known methods.

(Step 3) Unvulcanized rubber was adhered to the etched substrate (mold),the unvulcanized rubber is vulcanized, and the fine ridged/groovedstructure is transferred to the rubber surface (transferring step).

Unvulcanized rubber is placed on a silicon mold, is softened at 80° C.for 10 minutes and then, is pressed and vulcanized at 160° C. for 10minutes.

After vulcanization, the vulcanized rubber is peeled off from thesilicon mold, and the transfer of the fine ridged/grooved structure tothe rubber surface is confirmed. The region in which the fineridged/grooved structure is formed is visually recognizable due to beingcolored differently from the other regions (flat regions) on the rubbersurface, that is, the structural color of the fine ridged/groovedstructure.

A durability test is performed on the logo mark 204 thus formed in thestructural color, and a logo mark printed using an inkjet printeraccording to the conventional art. Specifically, surfaces (rubbersurfaces) of the logo marks thus formed are rubbed 100 times with acotton cloth, and the surface state and color change are visuallyobserved.

FIG. 3 shows results of the durability test. The table in FIG. 3 shows asample number, a color producing method, a ridge/groove height, avisually recognized color (color production), and a durability testresult. In columns of the durability test results, an unchanged samplein terms of the surface state and color is designated as “Pass”, and adecolorized sample is designated as “Fail”.

As illustrated in FIG. 3, after the durability test, the logo markprinted using the inkjet printer (Comparative Example 2) can not bevisually recognized due to peeling off of the ink, while there is nochange in visual state of the logo marks formed in structural colors(Examples 1 to 3 and Comparative Example 1).

In Comparative Example 1, among the logo marks formed in the structuralcolor, the ridge/groove height of the logo mark is 680 nm, which is outof range for producing the structural color described above (equal to orsmaller than 650 nm). Thus, no color is produced.

As has been described, in the vehicle tire 10 according to theembodiment, at least a part of the rubber member is indicated in thedifferent structural color from the colors of other regions, whichadvantageously improves the durability of indication on the rubbersurface compared to the drawing in ink or the like.

In addition, information may be displayed in any color on the surface ofthe rubber member by appropriately changing the arrangement pitch or theridge/groove height of the fine ridged/grooved portions 34.

In the present embodiment, the fine ridged/grooved portions 34 include acylindrical projection. However, no such limitation is intended, and thefine ridged/grooved portions may have various known shapes, which arecapable of producing the structural color. For example, the fineridged/grooved portions 34 may include a conical projection or agrid-like projection. Additionally, the fine ridged/grooved structure 30may include a hole or a grid-like groove formed on the rubber surface.Also in this case, the holes may be cylindrical or conical, andfurthermore, microparticles or the like may be arranged on the bottomportion of the conical hole (apex of the cone).

In the present embodiment, the example of the rubber member according tothe present technology applied to the vehicle tire is described.However, no such limitation is intended, and the rubber member accordingto the present technology is suitable as various known rubber members,in particular, any member vulcanized in a manufacturing process.

In the present embodiment, only the logo mark 204 is indicated in thestructural color. However, no such limitation is intended, and otherinformation displayed on the sidewall portion 12 of the vehicle tire 10may be also indicated in the structural color. The fine ridged/groovedstructure 30 may be formed on the entire rubber member, such that theentire rubber member is visually recognizable in the structural color.

In the present embodiment, the present technology is applied toinformation indicated on the sidewall portion 12 of the vehicle tire 10.However, no such limitation is intended, and the present technology maybe applied to information indicated on other portions of the vehicletire 10.

1. A rubber member comprising: a fine ridged/grooved structure on atleast a part of a surface of the rubber member, the fine ridged/groovedstructure formed via transfer from a mold and having fine ridged/groovedportions arranged at a constant arrangement pitch; a region in which thefine ridged/grooved structure is provided being visually recognizable bya structural color different from colors of other regions.
 2. The rubbermember according to claim 1, wherein the arrangement pitch orridge/groove height of the fine ridged/grooved portions is determinedbased on a wavelength of visible light, the wavelength corresponding toa color visually recognizable as the structural color.
 3. The rubbermember according to claim 1, wherein the arrangement pitch orridge/groove height of the fine ridged/grooved portions is equal to orsmaller than 650 nm.
 4. A tire made of a rubber member described inclaim
 1. 5. The tire according to claim 4, wherein the fineridged/grooved structure is formed on a sidewall portion, and the regionin which the fine ridged/grooved structure is provided is formed in ashape to display predetermined information.
 6. The tire according toclaim 5, wherein the sidewall portion contains a diene rubber, a carbonblack, and a silica, and the diene rubber contains from 30 to 70 mass %of natural rubber and/or isoprene rubber, a nitrogen adsorption specificsurface area of the carbon black is from 20 to 60 m²/g, a content of thecarbon black is from 5 to 45 parts by mass per 100 parts by mass of thediene rubber, a content of the silica is from 15 to 55 parts by mass per100 parts by mass of the diene rubber, and a total content of the carbonblack and the silica is from 30 to 60 parts by mass per 100 parts bymass of the diene rubber.
 7. A method of manufacturing the rubber memberdescribed in claim 1, the method comprising: forming a mask on whichpattern structures are arranged at the constant pitch; arranging themask on a substrate made of a metal or a semiconductor material andetching the substrate; and adhering unvulcanized rubber to thesubstrate, vulcanizing the unvulcanized rubber to form vulcanizedrubber, and transferring the fine ridged/grooved structure to a surfaceof the vulcanized rubber.
 8. The method of manufacturing the rubbermember according to claim 7, further comprising determining thearrangement pitch of the fine ridged/grooved portions based on awavelength of visible light, the wavelength corresponding to the colorvisually recognizable as the structural color, wherein in the formingthe mask, the pitch of the pattern structures is determined based on thearrangement pitch determined in the determining the arrangement pitch.9. The method of manufacturing the rubber member according to claim 7,further comprising determining a ridge/groove height of the fineridged/grooved portions based on a wavelength of visible light, thewavelength corresponding to the color visually recognizable as thestructural color, wherein in the etching, an etching time of thesubstrate is appropriately controlled to match the ridge/groove heightof the ridged/grooved portions with the ridge/groove height determinedin the determining the ridge/groove height.
 10. The rubber memberaccording to claim 2, wherein the arrangement pitch or ridge/grooveheight of the fine ridged/grooved portions is equal to or smaller than650 nm.
 11. A tire made of a rubber member described in claim
 10. 12.The tire according to claim 11, wherein the fine ridged/groovedstructure is formed on a sidewall portion, and the region in which thefine ridged/grooved structure is provided is formed in a shape todisplay predetermined information.
 13. The tire according to claim 12,wherein the sidewall portion contains a diene rubber, a carbon black,and a silica, and the diene rubber contains from 30 to 70 mass % ofnatural rubber and/or isoprene rubber, a nitrogen adsorption specificsurface area of the carbon black is from 20 to 60 m²/g, a content of thecarbon black is from 5 to 45 parts by mass per 100 parts by mass of thediene rubber, a content of the silica is from 15 to 55 parts by mass per100 parts by mass of the diene rubber, and a total content of the carbonblack and the silica is from 30 to 60 parts by mass per 100 parts bymass of the diene rubber.
 14. A method of manufacturing the rubbermember described in claim 10, the method comprising: forming a mask onwhich pattern structures are arranged at the constant pitch; arrangingthe mask on a substrate made of a metal or a semiconductor material andetching the substrate; and adhering unvulcanized rubber to thesubstrate, vulcanizing the unvulcanized rubber, and transferring thefine ridged/grooved structure to a surface of the vulcanized rubber. 15.The method of manufacturing the rubber member according to claim 14,further comprising determining the arrangement pitch of the fineridged/grooved portions based on a wavelength of visible light, thewavelength corresponding to the color visually recognizable as thestructural color, wherein in the forming the mask, the pitch of thepattern structures is determined based on the arrangement pitchdetermined in the determining the arrangement pitch.
 16. The method ofmanufacturing the rubber member according to claim 14, furthercomprising determining the ridge/groove height of the fineridged/grooved portions based on a wavelength of visible light, thewavelength corresponding to the color visually recognizable as thestructural color, wherein in the etching, an etching time of thesubstrate is appropriately controlled to match the ridge/groove heightof the ridged/grooved portions with the ridge/groove height determinedin the determining the ridge/groove height.